AAGA: Study identifies risk factors and consequences for patients
LONDON, UK: Accidental awareness is one of the most feared complications of general anaesthesia for both patients and anaesthetists. Patients in the UK and Ireland report this failure of general anaesthesia in approximately 1 in every 19,000 cases, according to the latest research. Accidental awareness during general anaesthesia (AAGA) is when general anaesthesia is intended but the patient remains conscious. The incidence of patient reports of awareness is much lower than previous estimates of awareness, which were as high as 1 in 600.
The findings come from the largest ever study of awareness, the Fifth National Audit Project (NAP5), which has been conducted over the last three years by the Royal College of Anaesthetists and the Association of Anaesthetists of Great Britain and Ireland. The researchers studied three million general anaesthetics from every public hospital in UK and Ireland, and studied more than 300 new reports of AAGA.
The extensive study showed that the majority of episodes of awareness are short-lived, occur before surgery starts or after it finishes, and do not always cause concern for patients. However, 51 per cent of episodes led to distress and 41 per cent to longer-term psychological harm. Sensations experienced included tugging, stitching, pain, paralysis and choking. Patients described feelings of dissociation, panic, extreme fear, suffocation and even dying. Longer-term psychological harm often included features of post-traumatic stress disorder.
The researchers found that longer-term adverse effects are closely linked with patients experiencing a sensation of paralysis during their awareness. The muscle relaxants used to stop muscles working, which is often needed for safe surgery, are responsible for this feeling. Distress at the time of the experience appears to be significant in the development of later psychological symptoms.
Prof. Jaideep Pandit, consultant anaesthetist at the Oxford University Hospitals NHS Trust and clinical lead , explained: “NAP5 is patient focussed, dealing as it does entirely with patient reports of AAGA. Risk factors were complex and varied, and included those related to drug type, patient characteristics and organisational variables. We found that patients are at higher risk of experiencing AAGA during caesarean section and cardiothoracic surgery, if they are obese or when there is difficulty managing the airway at the start of anaesthesia. The use of some emergency drugs heightens risk, as does the use of certain anaesthetic techniques. However, the most compelling risk factor is the use of muscle relaxants, which prevent the patient moving. Significantly, the study data also suggest that although brain monitors designed to reduce the risk of awareness have a role with certain types of anaesthetic, the study provides little support for their widespread use.”
Prof. Tim Cook, consultant anaesthetist at the Royal United Hospital Bath NHS Trust and co-author of the report, commented: “NAP5 has studied outcomes from all anaesthetics in five countries for a full year, making it a uniquely large and broad project. It is reassuring that the reports of awareness in NAP5 are a lot rarer than incidences in previous studies. The project dramatically increases our understanding of anaesthetic awareness and highlights the range and complexity of patient experiences. NAP5, as the biggest ever study of this complication, has been able to define the nature of the problem and those factors that contribute to it more clearly than ever before. As well as adding to the understanding of the condition, we have also recommended changes in practice to minimise the incidence of awareness and, when it occurs, to ensure that it is recognised and managed in such a way as to mitigate longer-term effects on patients.”
The project report includes clear recommendations for changes in clinical practice. Two main recommendations are the introduction of a simple anaesthesia checklist to be performed before the start of every operation, and the introduction of a structured approach to the management of patients who have reported awareness (specifically, the NAP5 Awareness Support Pathway). These two interventions are intended to decrease the errors that cause awareness and to minimise the psychological consequences when AAGA occurs.
It is anticipated that the findings of NAP5 will lead to changes in the practice of individual anaesthetists, their training, and hospital support systems, both nationally and internationally.
The report, titled “Accidental awareness during general anaesthesia in the United Kingdom and Ireland”, can be downloaded from the National Audit Project website at http://nap5.org.uk/NAP5report .
A shortened version, titled “The 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: Protocol, methods and analysis of data”, was published in the October issue of the Anaesthesia journal and of the British Journal of Anaesthesia .